Systems and methods for controlling operation of a reduced pressure therapy system to detect leaks

ABSTRACT

In some embodiments, a negative pressure apparatus includes a negative pressure source configured to provide negative pressure via a fluid flow path to a wound dressing placed to create a seal over a wound, a pressure sensor, and a controller. The controller can be configured to operate the negative pressure source in a first mode and determine a change in pressure in the fluid flow path over a period of time based on a plurality of measurements by the pressure sensor. In response to a determination that pressure in the fluid flow path is decreasing, the controller can operate the negative pressure source in a second mode in which greater amount of negative pressure is provided than in the first mode. In response to a determination that pressure in the fluid flow path is not decreasing, the controller can provide an indication of a first leak in the seal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/382,126, filed on Aug. 31, 2016, which is incorporated byreference it its entirety and is made part of this disclosure.

BACKGROUND Field

Embodiments of the present disclosure relate to methods and apparatusesfor dressing and treating a wound with topical negative pressure (TNP)therapy. In particular, but without limitation, embodiments disclosedherein relate to negative pressure therapy pumps and dressings, andmethods and systems for controlling the operation of TNP systems.

Description of the Related Art

Many different types of wound dressings are known for aiding in thehealing process of a human or animal. These different types of wounddressings include many different types of materials and layers, forexample, gauze, pads, foam pads or multi-layer wound dressings. Topicalnegative pressure (TNP) therapy, sometimes referred to as vacuumassisted closure, negative pressure wound therapy, or reduced pressurewound therapy, is widely recognized as a beneficial mechanism forimproving the healing rate of a wound. Such therapy is applicable to abroad range of wounds such as incisional wounds, open wounds andabdominal wounds or the like.

TNP therapy assists in the closure and healing of wounds by reducingtissue oedema; encouraging blood flow; stimulating the formation ofgranulation tissue; removing excess exudates and may reduce bacterialload and thus, infection to the wound. Furthermore, TNP therapy permitsless outside disturbance of the wound and promotes more rapid healing.

SUMMARY

The present disclosure relates to methods and apparatuses for dressingand treating a wound with reduced pressure therapy or topical negativepressure (TNP) therapy. In particular, but without limitation,embodiments of this disclosure relate to negative pressure therapyapparatuses, methods for controlling the operation of TNP systems, andmethods of using TNP systems. The methods and apparatuses canincorporate or implement any combination of the features describedbelow.

In some embodiments, a negative pressure wound therapy apparatusincludes a negative pressure source configured to provide negativepressure via a fluid flow path to a dressing placed over a wound tocreate a seal over the wound, a pressure sensor configured to measurepressure in the fluid flow path, and a controller. A controller can beconfigured to, in response to a request to initiate or restartapplication of negative pressure, operate the negative pressure sourcein a first mode and determine a change in pressure in the fluid flowpath over a period of time based on a plurality of measurements by thepressure sensor over the period of time. The controller can also beconfigured to, in response to a determination that pressure in the fluidflow path is decreasing, operate the negative pressure source in asecond mode in which the negative pressure source provides a greateramount of negative pressure than in the first mode. The controller canalso be configured to, in response to a determination that pressure inthe fluid flow path is not decreasing, provide an indication of a firstleak in the seal.

The apparatus of the preceding paragraph can include one or more of thefollowing features. The request to initiate or restart application ofnegative pressure can be associated with a negative pressure set pointto be established in the fluid flow path. Operation of the negativepressure source in the first mode can be insufficient to reduce pressurein the fluid flow path to establish the negative pressure set point.Operation of the negative pressure source in the second mode can besufficient to reduce pressure in fluid flow path to establish thenegative pressure set point.

The apparatus of any of the preceding paragraphs can include one or moreof the following features. Operation of the negative pressure in thesecond mode can include the controller being further configured toactivate the negative pressure source to reduce pressure in the fluidflow path to the negative pressure set point; if pressure in the fluidflow path has not reached the negative pressure set point over a firstperiod of time, deactivate the negative pressure source for a secondperiod of time; and in response to a determination that the secondperiod of time has elapsed, activate the negative pressure source toreduce pressure in the fluid flow path to establish the negativepressure set point.

The apparatus of any of the preceding paragraphs can include one or moreof the following features. The controller can be further configured tomonitor a number of deactivations of the negative pressure source forthe second period of time. The controller can be further configured toprovide an indication of a second leak in the seal in response to adetermination that the number of the negative pressure source exceeds aretry threshold. The first leak can be a leak of smaller intensity thanthe second leak. Indication of at least one of the first or second leaksin the seal can include deactivation of the source of negative pressure.Operation of the negative pressure source in the first mode can includeestablishment of a flow rate of about 25 mL/min in the fluid flow path.Indication of the first leak in the seal can correspond to an indicationof a leak with flow of about 25 mL/min or less.

The apparatus of any of the preceding paragraphs can include one or moreof the following features. The controller can be configured to determinethe change in pressure in the fluid flow path based on a determinationof a difference in a first pressure in the fluid flow path measured bythe pressure sensor and a second pressure in the fluid flow pathsubsequently measured by the pressure sensor. The first mode can be alow flow mode. The controller can be configured to operate the negativepressure source in the first mode based on a first drive signal providedto an actuator of the negative pressure source. The controller can beconfigured to operate the negative pressure source in the second modebased on a second drive signal provided to the actuator of the negativepressure source, the second drive signal being different from the firstdrive signal.

In some embodiments, a method of operating a negative pressure woundtherapy apparatus includes, by a controller, in response to a request toinitiate or restart application of negative pressure, operating anegative pressure source in a first mode. The negative pressure sourcecan be configured to provide negative pressure via a fluid flow path toa dressing placed over a wound to create a seal over the wound. Themethod can also include determining a change in pressure in the fluidflow path over a period of time based on a plurality of measurements bya pressure sensor over the period of time. The method can also include,in response to determining that pressure in the fluid flow path isdecreasing, operating the negative pressure source in a second mode inwhich the negative pressure source provides a greater amount of negativepressure than in the first mode. The method can also include, inresponse to determining that pressure in the fluid flow path is notdecreasing, providing an indication of a first leak in the seal.

The method of the preceding paragraph can include one or more of thefollowing features. The request to initiate or restart application ofnegative pressure can be associated with a negative pressure set pointto be established in the fluid flow path. Operating the negativepressure source in the first mode can be insufficient to reduce pressurein the fluid flow path to establish the negative pressure set point.Operating the negative pressure source in the second mode can besufficient to reduce pressure in fluid flow path to establish thenegative pressure set point.

The method of any of the preceding paragraphs can include one or more ofthe following features. Operating the negative pressure in the secondmode further includes: activating the negative pressure source to reducepressure in the fluid flow path to the negative pressure set point; ifpressure in the fluid flow path has not reached the negative pressureset point over a first period of time, deactivating the negativepressure source for a second period of time; and in response todetermining that the second period of time has elapsed, activating thenegative pressure source to reduce pressure in the fluid flow path toestablish the negative pressure set point.

The method of any of the preceding paragraphs can include one or more ofthe following features. The method can include monitoring a number ofdeactivations of the negative pressure source for the second period oftime. The method can include providing an indication of a second leak inthe seal in response to determining that the number of the negativepressure source exceeds a retry threshold. The first leak can be a leakof smaller intensity than the second leak. Indication of at least one ofthe first or second leaks in the seal can include deactivating thesource of negative pressure. Operating the negative pressure source inthe first mode can include establishing a flow rate of about 25 mL/minin the fluid flow path. Indication of the first leak in the seal cancorrespond to an indication of a leak with flow of about 25 mL/min orless.

The method of any of the preceding paragraphs can include one or more ofthe following features. Determining the change in pressure in the fluidflow path can be further based on determining a difference in a firstpressure in the fluid flow path measured by the pressure sensor and asecond pressure in the fluid flow path subsequently measured by thepressure sensor. The first mode can be a low flow mode. Operating thenegative pressure source in the first mode can further include providinga first drive signal to an actuator of the negative pressure source.Operating the negative pressure source in the second mode can furtherinclude providing a second drive signal to the actuator of the negativepressure source, the second drive signal being different from the firstdrive signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will now be described hereinafter,by way of example only, with reference to the accompanying drawings inwhich:

FIG. 1 illustrates an embodiment of a reduced pressure wound therapyapparatus including a pump, a dressing, and a conduit.

FIG. 2 illustrates a top level state diagram of operation of a negativepressure source according to some embodiments.

FIG. 3 illustrates an operational state diagram of operation of anegative pressure source according to some embodiments.

FIG. 4 illustrates another operational state diagram of operation of anegative pressure source according to some embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Embodiments disclosed herein relate to apparatuses and methods oftreating a wound with reduced pressure. As is used herein, reduced ornegative pressure levels, such as −X mmHg, represent pressure levelsrelative to normal ambient atmospheric pressure, which can correspond to760 mmHg (or 1 atm, 29.93 inHg, 101.325 kPa, 14.696 psi, etc.). In someembodiments, local ambient atmospheric pressure is used as a referencepoint, and such local atmospheric pressure may not necessarily be, forexample, 760 mmHg. Accordingly, a negative pressure value of −X mmHgreflects absolute pressure that is X mmHg below, for example, 760 mmHgor, in other words, pressure of (760-X) mmHg. In addition, negativepressure that is “less” or “smaller” than X mmHg corresponds to pressurethat is closer to atmospheric pressure (such as, −40 mmHg is less than−60 mmHg). Negative pressure that is “more” or “greater” than −X mmHgcorresponds to pressure that is further from atmospheric pressure (suchas, −80 mmHg is more than −60 mmHg).

The negative pressure range for some embodiments of the presentdisclosure can be approximately −80 mmHg, or between about −20 mmHg and−200 mmHg or more. Note that these pressures are relative to normalambient atmospheric pressure, which can be 760 mmHg. Thus, −200 mmHgwould be about 560 mmHg in practical terms. In some embodiments, thepressure range can be between about −40 mmHg and −150 mmHg.Alternatively a pressure range of up to −75 mmHg, up to −80 mmHg or over−80 mmHg can be used. Also in other embodiments a pressure range ofbelow −75 mmHg can be used. Alternatively, a pressure range of overapproximately −100 mmHg, or even −150 mmHg, can be supplied by thenegative pressure apparatus.

Embodiments of the present disclosure are generally applicable to use intopical negative pressure (“TNP”) therapy systems. Briefly, negativepressure wound therapy assists in the closure and healing of many formsof “hard to heal” wounds by reducing tissue oedema, encouraging bloodflow and granular tissue formation, and/or removing excess exudate andcan reduce bacterial load (and thus infection risk). In addition, thetherapy allows for less disturbance of a wound leading to more rapidhealing. TNP therapy systems can also assist in the healing ofsurgically closed wounds by removing fluid and by helping to stabilizethe tissue in the apposed position of closure. A further beneficial useof TNP therapy can be found in grafts and flaps where removal of excessfluid is important and close proximity of the graft to tissue isrequired in order to ensure tissue viability.

Reduced Pressure Therapy Systems and Methods

FIG. 1 illustrates an embodiment of a reduced pressure wound treatmentapparatus 100 comprising a wound dressing 102 in combination with anegative pressure source 104, which is illustrated as a pump assembly.In any of the apparatus embodiments disclosed herein, as in theembodiment illustrated in FIG. 1, the negative pressure source can be acanisterless negative pressure source (meaning that the negativepressure source does not have an exudate or liquid collection canister).However, any of the embodiments disclosed herein can be configured toinclude or support a canister. Additionally, in any of the apparatusembodiments disclosed herein, any of the negative pressure sourceembodiments can be mounted to, embedded within, or supported by thedressing, or adjacent to the dressing. The dressing 102 may be placedover a wound (not illustrated), and a conduit 106 may then be connectedto the dressing 102. Dressing 102 or any other dressing disclosed hereincan have be made of any suitable materials, sizes, components, etc. Theconduit 106 or any other conduit disclosed herein can be formed frompolyurethane, PVC, nylon, polyethylene, silicone, or any other suitablematerial.

Some embodiments of the dressing 102 can have a port 108 configured toreceive an end of the conduit 106 (e.g., the first end 106 a of theconduit 106), though such port 108 is not required. In some embodiments,the conduit can otherwise pass through and/or under the dressing 108 tosupply a source of reduced pressure to a space between the dressing 102and the wound so as to maintain a desired level of reduced pressure insuch space. Some embodiments of the apparatus 100 can be configured suchthat the first end 106 a of the conduit 106 is pre-attached to the port108. The conduit 106 can be any suitable article configured to provideat least a substantially sealed fluid flow pathway between the negativepressure source 104 and the dressing 102, so as to supply the reducedpressure provided by the negative pressure source 104 to the dressing102. In some embodiments, the port 108 can be made of soft, flexiblematerials such that, for example, the user would experience little or nodiscomfort if the user lies or otherwise puts pressure on the dressing102 and/or the port 108.

The dressing 102 can be provided as a single article with all wounddressing elements (including the port 108) pre-attached and integratedinto a single unit. The wound dressing 102 may then be connected, viathe conduit 106, to a source of negative pressure such as the negativepressure source 104. In some embodiments, though not required, thenegative pressure source 104 can be miniaturized and portable, such asthe PICO™ pump, although larger conventional pumps, such as the EZ CARE™pump, can also be used with the dressing 102. The pump can be adiaphragm pump (or any other type of negative pressure pump) actuated byan electric motor, a voice-coil actuator, a piezoelectric actuator, etc.

The wound dressing 102 can be located over a wound site to be treated.The dressing 102 can form a substantially sealed cavity or enclosureover the wound site. It will be appreciated that throughout thisspecification reference is made to a wound. In this sense it is to beunderstood that the term wound is to be broadly construed andencompasses open and closed wounds in which skin is torn, cut orpunctured or where trauma causes a contusion, or any other surficial orother conditions or imperfections on the skin of a patient or otherwisethat benefit from reduced pressure treatment. A wound is thus broadlydefined as any damaged region of tissue where fluid may or may not beproduced. Examples of such wounds include, but are not limited to, acutewounds, chronic wounds, surgical incisions and other incisions, subacuteand dehisced wounds, traumatic wounds, flaps and skin grafts,lacerations, abrasions, contusions, burns, diabetic ulcers, pressureulcers, stoma, surgical wounds, trauma and venous ulcers or the like. Insome embodiments, the components of the TNP system described herein canbe particularly suited for incisional wounds that exude a small amountof wound exudate.

In some embodiments, it may be preferable for the wound site to befilled partially or completely with a wound packing material. This woundpacking material is optional, but may be desirable in certain wounds,for example deeper wounds. The wound packing material can be used inaddition to the wound dressing 102. The wound packing material generallycan comprise a porous and conformable material, for example foam(including reticulated foams), and gauze. Preferably, the wound packingmaterial is sized or shaped to fit within the wound site so as to fillany empty spaces. The wound dressing 102 can then be placed over thewound site and wound packing material overlying the wound site. When awound packing material is used, once the wound dressing 102 is sealedover the wound site, TNP is transmitted from a pump through the wounddressing 102, through the wound packing material, and to the wound site.This negative pressure draws wound exudate and other fluids orsecretions away from the wound site.

In some embodiments, the tubing 106 can have a connector 112 positionedat a second end 106 b of the tubing 106. The connector 112 can beconfigured to couple with a short length of conduit 114 projecting fromthe negative pressure source 104, with a mating connector 114 a incommunication with the short length of conduit 114, with a connectorsupported by the pump housing, or otherwise. The length of the tubing114 in some embodiments can be approximately 14 mm (0.55 in), or fromapproximately 0.5 in to approximately 5 inches. The short length ofconduit or tubing 114 can decrease the discomfort to a patient whilelaying or otherwise resting on the pump and connector 112. Configuringthe negative pressure source 104 and tubing 106 so that the tubing 106can be quickly and easily removed from the negative pressure source 104can facilitate or improve the process of dressing or pump changes, ifnecessary. Any of the pump embodiments disclosed herein can beconfigured to have any of the connection configurations disclosed hereinbetween the tubing and the pump.

In some embodiments, as in the illustrated embodiment, the negativepressure source 104 can be of a sufficiently small and portable size tobe supported on a user's body or in a user's clothing or on the dressing102. For example, the negative pressure source 104 can be sized to beattached using adhesive medical tape or otherwise to a person's skin ina comfortable location, adjacent to or on the dressing 102 or otherwise.Further, the negative pressure source 104 can be sized to fit within aperson's pants or shirt pocket, or can be tethered to a person's bodyusing a lanyard, pouch, or other suitable device or article.

Some embodiments of the apparatus 100 are designed to operate withoutthe use of an exudate canister. The dressing 102 can be configured tohave a film having a high water vapour permeability to enable theevaporation of surplus fluid, and can have a superabsorbing materialcontained therein to safely absorb wound exudate. Some embodiments ofthe apparatus are designed for single-use therapy and can be disposed ofin an environmentally friendly manner after an approximately maximumusage of from seven to eleven days. The pump can be programmed toautomatically terminate therapy after a desired number of days, e.g.,after seven days, further operation of the pump will not be possible.Some embodiments are designed for longer or repeated usage, and can beconfigured to support an exudate canister.

In some embodiments, the system 100 provides indication, alarms, etc. tothe user reflecting operating conditions. The system 100 can includevisual, audible, tactile, and other types of indicators and/or alarmsconfigured to signal to the user various operating conditions. Suchconditions include system on/off, standby, pause, normal operation,dressing problem, leak, error, and the like. The indicators and/oralarms can include one or more speakers, displays, light sources, etc.,and/or combinations thereof. For example, indication can be provided byactivating or deactivating the source of negative pressure, reducingnegative pressure level generated by the source of negative, loweringthe amount of power used by the source of negative pressure, etc. or anycombination thereof.

As is illustrated in FIG. 1, indicators 123 can be one or more lightemitting diodes (LEDs). The indicators 123 can be positioned on ahousing 120 of the negative pressure source 104 and can be configured toalert a user to a variety of operating and/or failure conditions of thenegative pressure source, including alerting the user to normal orproper operating conditions, pump failure, power supplied to the pump orpower failure, the condition or voltage level of the batteries,detection of a leak within the dressing (e.g., in the seal) or flowpathway, suction blockage, or any other similar or suitable conditionsor combinations thereof. In some embodiments, the indicators 123 caninclude a battery indicator, an OK indicator, and a dressing indicator.The negative pressure source 104 can also have a control button 122(which can also be a switch or other similar component).

The fluidic connection between the dressing 102 and the negativepressure source 120 can be referred to as the fluid flow path.

In some embodiments, such as when the negative pressure source 104 ismounted to or embedded within the dressing 102, portions of or theentirety of one or more of the conduit 106, the port 108, the connector112, or the conduit 114 can be omitted.

In some embodiments, the negative pressure source 104 is controlled byat least one controller, which can be coupled to at least one memory.

Systems and Methods for Controlling the Negative Pressure Source toDetect Leaks

In some embodiments, the negative pressure source 104 can be configuredto control the operation of system. For example, the negative pressuresource 104 can be configured to provide a suitable balance betweenuninterrupted delivery of therapy and/or avoidance of inconveniencingthe user by, for example, frequently or needlessly pausing or suspendingtherapy and a desire to conserve power, limit noise and vibrationgenerated by the negative pressure source, etc. FIG. 2 illustrates a toplevel state diagram 1200 of operation of the negative pressure sourceaccording to some embodiments. In some embodiments, a controller of thenegative pressure source can be configured to implement the flow of thestate diagram 1200. As is illustrated in FIG. 2, the operation of thenegative pressure source can, in some embodiments, be grouped into fourgeneral state categories: inactive/initialization (states 1206 and1202), active 1210, operational 1250, and end of life (state 1214). Asis illustrated in FIGS. 2 and 3, state categories 1210 and 1250 eachcomprises multiple states and transitions between states.

In some embodiments, so long as a power source (e.g., one or morebatteries) is not connected to the negative pressure source or removed(as is illustrated by the transition 1204), or the negative pressuresource has not been activated (e.g., by pulling an activation strip,triggering a switch, or the like), the negative pressure source remainsin state 1206. While remaining in this state, the negative pressuresource can remain inactive. When the power source is connected and/orthe negative pressure source has been activated for a first time, thenegative pressure source transitions to state 1202, where power onself-test(s) (POST) can be performed. Power on self-test(s) can includeperforming various checks to ensure proper functionality of the system,such as testing a memory (e.g., performing a check, such as a cyclicredundancy check, of the program code to determine its integrity,testing the random access memory, etc.), reading a pressure sensor todetermine whether the pressure values are within suitable limits,reading the remaining capacity or life of the power source (e.g.,battery voltage, current, etc.) to determine whether it is withinsuitable limits, testing the negative pressure source, and the like. Asis illustrated, indicators (e.g., one or more LEDs, one or more LCDs,etc.) can be configured to indicate to the user (e.g., by blinking orflashing once) that the negative pressure source is undergoing POSTtest(s).

In some embodiments, if one or more of POST test(s) fail, the negativepressure source can transition to non-recoverable error state 1214.While in this state, the negative pressure source can deactivatetherapy, and the indicators 123 can be configured and indicate to theuser that an error was encountered. In some embodiments, all indicatorscan be configured to remain active. Based on the severity of error, insome embodiments, the negative pressure source can be configured torecover from the error and continue operation (or transition to thenon-recoverable error state 1214). As is illustrated, the negativepressure source can transition to state 1214 upon encountering a fatalerror during operation. Fatal errors can include program memory errors,program code errors (e.g., encountering an invalid variable value),controller operation errors (e.g., watchdog timer expires without beingreset by the controller), component failure (e.g., inoperative negativepressure source, inoperative pressure sensor, etc.), and any combinationthereof.

When POST test(s) pass, in some embodiments, the negative pressuresource can transition to a manually paused state 1216. As isillustrated, this transition can be indicated to the user bydeactivating one of indicators 123 (e.g., the battery indicator). Whenthe negative pressure source transitions into and remains in themanually paused state 1216, the user can be provided an indication, suchas by deactivating one or more indicators (e.g., the OK indicator andthe dressing indicator). In some embodiments, therapy can be suspendedwhile the negative pressure source remains in the manually paused state1216. For example, the source of negative pressure (e.g., pump) can bedeactivated (or turned off). In some embodiments, indication can beprovided by deactivating the source of negative pressure.

In some embodiments, the negative pressure source can be configured tomake a transition 1224 from the manually paused state 1216 to theoperational state category 1250 (where the negative pressure source isconfigured to deliver therapy) in response to receiving a signal fromthe switch. For example, the user can press a button to start, suspend,and/or restart therapy. In some embodiments, the negative pressuresource can be configured to monitor the duration of time the negativepressure source remains in the manually paused state 1216. This can beaccomplished, for example, by maintaining a timer (in firmware,software, hardware or any combination thereof), which can be reset andstarted when the negative pressure source transitions into the manuallypaused state 1216. The negative pressure source can be configured toautomatically make the transition 1224 from the manually paused state1216 to the operational state category 1250 when the time durationexceeds a threshold. In some embodiments, such threshold can be a presetvalue, such as between 1 minute or less and 1 hour or more. In someembodiments, the threshold can be set or changed by the user. In someembodiments, the threshold can be varied based on various operatingconditions or on any combination thereof. For example, as the negativepressure source nears the end of life (as is explained below), thethreshold can be decreased. In some embodiments, the user can pausetherapy by activating the switch (e.g., pressing the button), therebycausing the negative pressure source to make a transition 1222 from theoperational state category 1250 to the manually paused state 1216. Insome embodiments, the negative pressure source can be configured so thatthe user can only pause therapy, whereas disconnecting the power source(e.g., removing batteries) stops therapy.

In some embodiments, the negative pressure source can be configured toinclude a paused state 1218. When the negative pressure sourcetransitions into and remains in the paused state 1218, the user can beprovided an indication. For example, the negative pressure source can beconfigured to deactivate the OK indicator and cause the dressingindicator to flash or blink. In some embodiments, therapy can besuspended while the negative pressure source remains in the manuallypaused state 1216. For example, the source of negative pressure (e.g.,pump) can be deactivated (or turned off), which provides the indicationto the user that the negative pressure source is in the paused state1218. As is explained below, in some embodiments, the negative pressuresource can be configured to transition from the operational statecategory 1250 into the paused state 1218 when a number of retry cyclesexceeds a retry limit (transition 1228) or when duty cycle is determinedto exceed a duty cycle limit (transition 1230). In some embodiments,transitions 1228 and 1230 can reflect the presence of a leak in thesystem.

In some embodiments, the negative pressure source can be configured tomake a transition 1226 from the paused state 1218 to the operationalstate category 1250 (where the negative pressure source is configured toactivate the pump to deliver therapy) in response to receiving a signalfrom the switch (e.g., the user pressing a button to restart therapy).In some embodiments, the negative pressure source can be configured tomonitor the duration of time the negative pressure source remains in thepaused state 1218. For example, this can be accomplished by maintaininga timer (in firmware, software, hardware or any combination thereof),which can be reset and started when the negative pressure sourcetransitions into the paused state 1218. The negative pressure source canbe configured to automatically make the transition 1226 from the pausedstate 1218 to the operational state category 1250 when the time durationexceeds a threshold. The threshold can be the same or different than thethreshold of the manually paused state 1216 described herein. In someembodiments, the threshold can be a preset value, such as between 1minute or less and 1 hour or more. In some embodiments, the thresholdcan be set or changed by the user. In some embodiments, the thresholdcan be varied based on various operating conditions or on anycombination thereof. For example, as the negative pressure source nearsthe end of life (as is explained below), the threshold can be decreased.

In some embodiments, the negative pressure source includes both themanually paused state 1216 and the paused state 1218 in order todifferentiate between various causes for pausing therapy. Such abilityto differentiate can allow the negative pressure source to provide theuser with an indication of a particular cause for pausing therapy (e.g.,manually paused state 1216 and paused state 1218 can provide differentindications). For example, therapy can be paused due to the usermanually pressing the button, in which case the negative pressure sourcecan make the transition 1222 from the operational state category 1250 tothe manually paused state 1216. As another example, therapy can bepaused due to detecting a leak, in which case the negative pressuresource can make the transition 1228 and/or 1230 from the operationalstate category 1250 to the paused state 1218. In some embodiments, thenegative pressure source can be configured to include one stateindicating a suspension or pause in the delivery of therapy or more thantwo such states.

In some embodiments, the negative pressure source can be configured tomonitor the remaining capacity or life of the power source (e.g., byperiodically reading or sampling the battery voltage, current, etc.).The negative pressure source can be configured to indicate to the userthe remaining capacity. For example, if the power source is determinedto have a normal remaining capacity (e.g., as a result of comparison toa threshold, such as 2.7V, 2.6V, 2.5V, etc.), the battery indicator canbe deactivated. If the power source is determined to have low remainingcapacity, the negative pressure source can be configured to provide anindication to the user by, for example, causing the battery indicator toblink or flash, as is illustrated by the transition 1220. In someembodiments, the battery indicator can be configured to be blinking orflashing intermittently or continuously regardless of the state thenegative pressure source is in or only in particular states.

In some embodiments, when the remaining capacity of the power source isdetermined to be at or near a critical level (e.g., as a result ofcomparison to a threshold, such as 2.4V, 2.3V, 2.2V, etc.), the negativepressure source can be configured to transition into a battery criticalstate 1212. In some embodiments, the negative pressure source can beconfigured to remain in this state until the capacity of the powersource is increased, such as by replacing or recharging the powersource. The negative pressure source can be configured to deactivatetherapy while remaining in the battery critical state 1212. In addition,as is illustrated, the negative pressure source can be configured toindicate to the user that the power source is at or near the criticallevel by, for example, deactivating all indicators.

In some embodiments, the negative pressure source can be configured toprovide therapy for a predetermined period of time, such asapproximately 1 day, 2-10 days, etc. following a first activation. Insome embodiments, such period of time can be a preset value, changed bythe user, and/or varied based on various operating conditions or on anycombination thereof. The negative pressure source can be disposed uponthe expiration of such period of time. In some embodiments, the firstactivation can be reflected by a transition into the active statecategory 1210, by pulling the activation strip (e.g., transition intostate 1202), etc. Once the negative pressure source has been activated,the negative pressure source can be configured to monitor the durationit has remained active. In some embodiments, the negative pressuresource can be configured to monitor the cumulative duration of remainingin the active state category 1210. This can be accomplished, forexample, by maintaining a timer (in firmware, software, hardware or anycombination thereof), that reflects such duration.

When the duration reaches or exceeds a threshold (e.g., 7 days, 10 days,etc.), the negative pressure source can be configured to transition toan end of life (EOL) state 1240. The negative pressure source can beconfigured to deactivate therapy while remaining in state 1240 and toindicate to the user that end of negative pressure source’ usable lifehas been reached. For example, the negative pressure source can beconfigured to deactivate all indicators and/or deactivate the button. Insome embodiments, when the negative pressure source is disposable,transitioning to the end of life state 1240 means that the negativepressure source can be disposed of. The negative pressure source can beconfigured to disable reactivation of the negative pressure source oncethe end of life has been reached. For example, the negative pressuresource can be configured to not allow reactivation even if the powersource is disconnected and reconnected later, which can be accomplishedby storing an indication, value, flag, etc. in the read only memory.

FIG. 3 illustrates the operational flow in state category 1250 of thenegative pressure source 104 according to some embodiments. The negativepressure source can be configured to deliver therapy, monitor leaks inthe system, provide indication(s) to the user, and the like. As isexplained below, in some embodiments, the negative pressure source canbe configured to deliver therapy by initially attempting to establish afirst set point or desired negative pressure level (e.g., negativepressure between −5 mmHg or less and −200 mmHg or more, such as −100mmHg) in the fluid flow path (e.g., under the dressing 102). In someembodiments, the first desired negative pressure level can be a presetvalue, set or changed by the user, and/or varied based on variousoperating conditions or on any combination thereof. Once the firstdesired negative pressure level is established in the fluid flow path,the negative pressure source can be configured to deactivate the sourceof negative pressure (e.g., pump). When negative pressure in the fluidflow path (e.g., under the dressing 102) decreases (e.g., gravitatestoward standard atmospheric pressure) due to leaks in the system, thenegative pressure source can be configured to restore negative pressurein the fluid flow path by activating the pump to establish a second setpoint or desired negative pressure level in the fluid flow path (e.g.,negative pressure between −5 mmHg or less and −200 mmHg or more, such as−100 mmHg). In some embodiments, the second desired negative pressurelevel can be a preset value, set or changed by the user, and/or variedbased on various operating conditions or on any combination thereof. Insome embodiments, the first and second desired negative pressure levelscan be the same. In some embodiments, the first and second desirednegative pressure levels can be different, that is, the second negativepressure level can be less than the first negative pressure level orvice versa.

In some embodiments, the negative pressure source can transition fromthe manually paused state 1216 and/or paused state 1218 to state 1252.As is explained herein, this transition can be caused by the userpressing the button to start/restart therapy and/or upon expiration ofduration of time, such as 1 hour. The negative pressure source can beconfigured to immediately transition to an initial pump down (IPD) state1260, where the negative pressure source can be activated to establishthe first desired negative pressure level in the fluid flow path. Insome embodiments, the negative pressure source can be activated if thepressure level in the fluid flow path is above (less than) the firstdesired negative pressure level. Activating the source of negativepressure to establish the first desired negative pressure level in thefluid flow path (e.g., under the dressing 102) can be referred to hereinas the “initial pump down.” The negative pressure source can beconfigured to indicate to the user that it is performing the initialpump down by, for example, causing the OK indicator to blink or flashand deactivating the dressing indicator. In some embodiments, theindication can be provided by, for example, activating the source ofnegative pressure. The negative pressure source can be configured tomeasure the level of pressure in the fluid flow path by reading orsampling the sensor. The pressure sensor can be positioned in anysuitable location in the fluid flow path, such as at or near the pumpinlet, under or near the dressing, etc. In some embodiments, more thanone pressure sensor is positioned in the fluid flow path such as, forexample, in different locations.

In some embodiments, the negative pressure source can be configured tomonitor the duration of time the negative pressure source remains in theIPD state 1260. This can be accomplished, for example, by maintaining atimer (in firmware, software, hardware or any combination thereof),which can be reset and started when the negative pressure sourcetransitions into the IPD state 1260. In some embodiments, in order toconserve power, limit the noise and/or vibration generated by the pump,etc., the negative pressure source can be configured to suspend theinitial pump down operation for a period of time and, later, retry theinitial pump down. This functionality can, for example, conserve batterypower and allow transient and/or non-transient leaks to become resolvedwithout user intervention or allow the user to fix the leak (e.g.,straighten the dressing, fix the seal, check the connection orconnections, etc.).

In some embodiments, when the duration of time for remaining in the IPDstate 1260 equals or exceeds a threshold (e.g., 30 seconds), thenegative pressure source can be configured to make the transition 1264to state 1266. In some embodiments, the threshold can be a preset value,such as between 5 seconds or lower and 5 minutes or higher. In someembodiments, the threshold can be set or changed by the user. In someembodiments, the threshold can be varied based on various operatingconditions or on any combination thereof. In some embodiments, thenegative pressure source can be configured to deactivate the pump whenmaking the transition 1264. The negative pressure source can beconfigured to monitor a number attempts (e.g., by maintaining a counterwhich can be reset in state 1252 and updated in wait state 1270) made toestablish the first desired negative pressure in the fluid flow path. Insome embodiments, the negative pressure source can be configured toprovide a limited or maximum number of IPD retry attempts in order, forexample, to conserve power. Preferably, the negative pressure source canbe configured to provide a limited number of consecutive IPD retryattempts, although the negative pressure source can be configured toprovide a limited number of non-consecutive IPD retry attempts or a mixof consecutive and non-consecutive IPD retry attempts. The threshold forIPD retry attempts can be 1, 2, 3, 4, 5, and so on. In some embodiments,the threshold can be a preset value. In some embodiments, the thresholdcan be set or changed by the user. In some embodiments, the thresholdcan be varied based on various operating conditions or on anycombination thereof.

In some embodiments, the negative pressure source can be configured todetermine in state 1266 whether the number of IPD retry attempts made isequal to or exceeds the threshold (e.g., 1 retry attempt). In case thenumber of IPD retry attempts made is equal or exceeds the threshold, thenegative pressure source can be configured to make the transition 1228 ato the paused state 1218, where therapy is paused or suspended as isdescribed herein. Otherwise, the negative pressure source can beconfigured to make the transition 1268 to the wait state 1270. In someembodiments, the negative pressure source can be configured todeactivate the source of negative pressure in state 1266, which canprovide an indication to the user that the negative pressure sourcetransitioned to state 1266.

In some embodiments, the negative pressure source can be configured todeactivate the pump in the wait state 1270, thereby pausing therapy fora period of time (e.g., between 1 second or less and 1 minute or more,such as 15 seconds). This can be accomplished, for example, bymaintaining a timer (in firmware, software, hardware or any combinationthereof), which can be reset and started when the negative pressuresource transitions into the wait state 1270. This period of time in thewait state 1270 can be preset or variable (e.g., automatically or by theuser). In some embodiments, the period of time can be varied based onvarious operating conditions or on any combination thereof. The periodof time the negative pressure source remains in the wait state 1270 canbe decreased or increased (e.g., multiplied by a factor between 0.1 orless and 4.0 or more, such as 2), on each transition into the wait state1270. The period of time can be decreased or increased on eachsuccessive transition into the wait state 1270. The period of time canbe decreased or increased until it equals or passes a threshold (e.g.,between 1 second or less and 5 minutes or more, such as 4 minutes). Inaddition, the period of time can be reset to an initial value upontransition to a monitor pressure state 1280, transition to the manuallypaused state 1216, transition to the paused state 1218, etc.

In some embodiments, the negative pressure source can be configured toindicate to the user that the negative pressure source is in the waitstate 1270. For example, the negative pressure source can be configuredto cause the OK indicator to flash or blink and deactivate the dressingindicator. In some embodiments, deactivating the pump can provideindication that the negative pressure source is in the wait state 1270.Upon expiration of the period of time in the wait state, the negativepressure source can be configured to make the transition 1272 from thewait state 1270 to the IPD state 1260, where the negative pressuresource can attempt to establish the first desired negative pressurelevel in the fluid flow path. In some embodiments, the negative pressuresource can be configured to ensure that the negative pressure levelunder the dressing remains above a certain safety level. For example,the negative pressure source can be configured to maintain the negativepressure level in the fluid flow path above a safety level between −150mmHg or less and −250 mmHg or more, such as −225 mmHg.

In some embodiments, the retry transitions (e.g., transitions 1264,1268, and 1272) between the IPD state 1260, state 1266, and the waitstate 1270 can detect a leak with high flow, such as a leak thatprevents the initial pump down. For example, the retry transitions candetect a leak with a flow of 30 scc/m (e.g., 30 mL/min or any lower orhigher suitable flow) or more. A leak having smaller flow may bedetected by the transitions (e.g., 1282 and 1284) between states 1280and 1290 as explained below, but such detection may take a long periodof time, such as 30 minutes or more. In certain cases, there is a needto detect a low flow leak quickly. For example, a healthcareprofessional that may place the dressing on the patient and activatedelivery of negative pressure therapy, may need to be quickly alertedthat there is a leak so that the healthcare professional can remedy theleak.

In some embodiments, a lower flow leak can be quickly detected by a leakcheck state 1259, which is entered from the IPD state 1260 (via atransition 1312) prior to initial pump down or directly from themanually paused state 1216 and/or the paused state 1218. In the leakcheck state 1259, the controller can operate the negative pressuresource to provide a lower flow rate in the fluid flow path than, forexample, in the IPD state 1260. While the flow rate provided by thenegative pressure source may not be sufficient to perform the initialpump down of the wound, the flow rate is nonetheless sufficient todetect if a low flow leak is present in the fluid flow path. Forexample, the negative pressure source can be configured to provide aflow rate of about 25 scc/m (e.g., 25 mL/min or any other lower orhigher suitable flow) in the leak check state 1316. While the negativepressure source operates in such low flow mode, the controller cananalyze the change in pressure in the fluid flow path (e.g., under thedressing) to identify signs of successful depressurization, such aswhether the pressure in the fluid flow path is decreasing, which isindicative of leak rate (e.g., in dressing seal) being below thenegative pressure flow rate and therefore within acceptable levels. Onthe other hand, if the pressure in the fluid flow path remains static ator below atmospheric pressure, this can be indicative of the leak ratebeing above the flow rate of the negative pressure source (e.g., 25scc/m or any other suitable lower or higher flow), which may not beacceptable.

The controller can analyze the change in pressure in the fluid flow pathbased on multiple pressure readings received from the pressure sensor.For example, a first pressure reading P₁ can be taken at time t₁ and asecond pressure reading P₂ can be taken at a subsequent time t₂. Timest₁ and t₂ can be a second or less or more apart. Based on the differencebetween pressure levels P₂ and P₁, the controller can determine if thepressure in the fluid flow path is decreasing (e.g., becoming morenegative). In some embodiments, more than two pressure readings can beused and multiple pressure readings can be further processed, such asaveraged, smoothed, low-pass filtered, etc., to minimize the risk ofmaking an erroneous determination. In some embodiments, change inpressure is analyzed over a period of time, such as 5 seconds or more orless.

In certain implementations, in response to detecting that a leak ispresent in the fluid flow path, the controller can provide one or moreindications to the user. For example, the controller can cause atransition 1316 to the pause state 1218, where therapy is paused orsuspended as is described herein. If the controller does not detectpresence of a leak, transition 1314 to the IPD state 1260 can be madeand the negative pressure source continues to operate as describedherein. In some embodiments, detection of a leak in the leak check state1259 can be performed in a minute or less. In some implementations,detection of a leak can be performed in 10 seconds or less, 30 secondsor less, etc.

In certain embodiments, the leak check state 1259 can be replaced bymeasuring the rate of pressure change in the fluid flow path when thenegative pressure source is deactivated, such as for example in the waitstate 1270. However, while the rate of decay of the negative pressure(toward atmospheric pressure) may indicate a presence of a leak, thevolume of the wound may need to be known in order to make an accuratedetermination. In some cases, the volume of the wound is not known apriori. Utilizing the leak check state 1259 as described herein mayprovide a solution that is independent of the wound volume. Becausefluid flow rates are analyzed as described herein, even though a largevolume would depressurize more slowly than a small one, the large woundvolume would still depressurize due to one or more leaks, which can bedetected as described herein.

In some embodiments, a negative pressure source can be calibrated tooperate in the leak check state 1259. For example, a drive signalsupplied to the actuator of the pump can be selected (e.g., duringcalibration in manufacturing, etc.) to cause the pump to provide lowflow to detect presence of a leak. The drive signal can be selected sothat it will not cause the pump to stall. A different drive signal canbe used in the IPD state.

In some embodiments, when the first desired negative pressure level inthe fluid flow path has been established, the negative pressure sourcecan be configured to make the transition 1276 to a monitor state 1280.The negative pressure source can be configured to reset the number ofIPD retry attempts when making the transition 1276. The negativepressure source can be configured to indicate the transition to themonitor state 1280 to the user by, for example, causing the OK indicatorto blink or flash and deactivating the dressing indicator. Whileremaining in the monitor state 1280, the negative pressure source can beconfigured to deactivate the pump (which can provide an indication tothe user that the negative pressure source is in the monitor state 1280)and periodically or continuously monitor the level of pressure in thefluid flow path. The negative pressure source can be configured tomeasure the level of pressure in the fluid flow path by reading orsampling the sensor.

In some embodiments, the negative pressure source can be configured todetermine whether, for example, due to leaks in the system, the level ofnegative pressure in the fluid flow path decreases to reach and/or pass(e.g., become less than) a threshold. The threshold can be selected fromthe range between −10 mmHg or less and −100 mmHg or more, such as −60mmHg. In some embodiments, the threshold can be a preset value, set orchanged by the user, and/or varied based on various operating conditionsor on any combination thereof. If the threshold is determined to bereached or passed, the negative pressure source can be configured torestore the level of negative pressure in the fluid flow path. In someembodiments, the negative pressure source can be configured toreestablish the first desired negative pressure level or establishanother, different negative pressure level. This can be accomplished bymaking the transition 1282 to a maintenance pump down (MPD) state 1290.

In some embodiments, the negative pressure source can be configured toactivate the pump to establish the desired level of negative pressure inthe fluid flow path (e.g., the first desired level) while the negativepressure source remains in the MPD state 1290. The negative pressuresource can be configured to provide an indication to the user, forexample, by causing the OK indicator to blink or flash and deactivatingthe dressing indicator. In some embodiments, the negative pressuresource activating the source of negative pressure can provide anindication to the user that the negative pressure source transitioned tostate 1290. In some embodiments, the negative pressure source can beconfigured to generate less noise and vibration when the pump isactivated in the MPD state 1290 than when the pump is activated in theIPD state 1264. For example, the difference in the noise level can bebetween 1 dB or less and 30 dB or more, such as approximately 7 dB,approximately 20 dB, etc. As another example, the difference in thenoise level can be between 30 dB or less to 80 dB or more, such asapproximately 45 dB, approximately 50 dB, approximately 65 dB, etc.

In some embodiments, the negative pressure source can be configured tomonitor the duration of time it remains in the MPD state 1290. This canbe accomplished, for example, by maintaining a timer (in firmware,software, hardware or any combination thereof), which can be reset andstarted when the negative pressure source makes the transition 1282 intothe MPD state 1290. In some embodiments, in order to conserve power,limit the noise and/or vibration generated by the pump, etc., thenegative pressure source can be configured to suspend the maintenancepump down operation for a period of time and, later, retry the initialpump down and/or maintenance pump down. This functionality can, forexample, conserve battery power and allow transient and/or non-transientleaks to become resolved without user intervention or allow the user tofix the leak (e.g., straighten the dressing, fix the seal, check theconnection or connections, etc.).

In some embodiments, when the duration of time in the MPD state 1290equals or exceeds a threshold (e.g., a value between 5 seconds or lowerand 5 minutes or higher, such as 10 seconds) and the pressure level inthe fluid flow path has not reached the desired negative pressure level,the negative pressure source can be configured to make the transition1292 to state 1294. The threshold can be a preset value, set or changedby the user, and/or varied based on various operating conditions or onany combination thereof. In some embodiments, the negative pressuresource can be configured to deactivate the pump when making thetransition 1292, which can provide an indication to the user that thenegative pressure source is making the transition. The negative pressuresource can be configured to monitor a number of MPD attempts (e.g., bymaintaining a counter which can be reset in the state 1252 and/or whenmaking the transition 1228 b and updated when making the transition1296) made to establish the desired negative pressure in the fluid flowpath. In some embodiments, the negative pressure source can beconfigured to provide a limited or maximum number of MPD retry attempts(e.g., to conserve power). Preferably, the negative pressure source canbe configured to provide a limited number of consecutive MPD retryattempts, although the negative pressure source can be configured toprovide a limited number of non-consecutive MPD retry attempts or a mixof consecutive and non-consecutive retry attempts. The threshold for MPDretry attempts can be 1, 2, 3, 4, 5, and so on. In some embodiments, thethreshold can be a preset value, set or changed by the user, and/orvaried based on various operating conditions or on any combinationthereof. The negative pressure source can be configured to set thenumber of IPD and MPD retry attempts to the same or different value. Thenegative pressure source can be configured to determine in state 1294whether the number of MPD retry attempts made is equal to or exceeds thethreshold (e.g., 3 retry attempts). In case the number of MPD retryattempts made is equal or exceeds the threshold, the negative pressuresource can be configured to make the transition 1228 b to the pausedstate 1218, where therapy is paused or suspended as is described herein.Otherwise, the negative pressure source can be configured to make thetransition 1296 to the wait state 1270, where therapy is paused orsuspended as is described herein. Alternatively, the negative pressuresource can be configured to make the transition to the IPD state 1260 orMPD state 1290.

In some embodiments, the negative pressure source can be configured tomake the transition 1284 to the monitor state 1280 if the level ofpressure under the dressing reaches or exceeds (e.g., become greaterthan) the desired negative pressure level. The negative pressure sourcecan also be configured to reset the number of MPD retry attempts whenmaking the transition 1284.

In some embodiments, the negative pressure source can be configured tomonitor the duty cycle of the source of negative pressure (e.g., pump).The negative pressure source can be configured to monitor the duty cycleperiodically and/or continuously. Duty cycle measurements can reflectvarious operating conditions of the system, such as presence and/orseverity of leaks, rate of flow of fluid (e.g., air, liquid and/or solidexudate, etc.) aspirated from wound, and so on. For example, duty cyclemeasurements can indicate presence of a high leak, and the negativepressure source can be configured to indicate this condition and/ortemporarily suspend or pause operation of the pump in order to conservepower. This functionality can, for example, conserve battery power andallow transient and/or non-transient leaks to become resolved withoutuser intervention or allow the user to fix the leak (e.g., straightenthe dressing, fix the seal, check the connection or connections, etc.).

In some embodiments, the negative pressure source can be configured toperiodically monitor the duty cycle, such as once between every 10seconds or less and 5 minutes or more. In some embodiments, the negativepressure source can be configured to monitor the duty cycle once perminute. This can be accomplished by maintaining a timer (in firmware,software, hardware or any combination thereof), which can be set toexpire every minute (e.g., as is indicated by an interrupt or viapolling) and can be restarted (e.g., by clearing an interrupt). In someembodiments, the time interval for measuring the duty cycle can be apreset value, set or changed by the user, and/or varied based on variousoperating conditions or on any combination thereof. In some embodiments,the negative pressure source can be configured to monitor the duty cyclewhen the negative pressure source is in the operational state category1250 (i.e., any of states 1260, 1266, 1270, 1280, 1290, 1294 and/or anytransitions between any of the states), as the negative pressure sourceis configured to activate the pump in this state category. In someembodiments, the negative pressure source can be configured to monitorthe duty cycle when the negative pressure source is in a particularstate and/or state transition or subset of states and/or statetransitions of the operational state category 1250. In some embodiments,the negative pressure source can be configured to monitor the duty cyclewhen the pump assembly is in a particular state and/or state transition,subset of states and/or state transitions, or all states and/or statetransitions of the active state category 1210 or any combination of anystates and/or state transitions disclosed herein. As is illustrated inFIG. 3, the negative pressure source can make the transition 1302 fromany of states 1260, 1266, 1270, 1280, 1290, 1294 and/or transitionsbetween any of the states to state 1300, where the negative pressuresource determines the duty cycle of the pump during the elapsed minute.The duty cycle can be determined according to the equation:

DC=t/T,  (1)

where DC is the duty cycle, t is the duration that the source ofnegative pressure is active, and T is the total time underconsideration. In case of monitoring the duty cycle once per minute(i.e., T=60 seconds), the duty cycle can be expressed (e.g., in percent)as:

DC=(Pump run time during the elapsed minute/60)*100%  (2)

In order to determine the duty cycle, the negative pressure source canbe configured to monitor the duration of time that the pump has beenactive (e.g., the pump run time) and/or inactive.

In some embodiments, the negative pressure source can be configured tocompare the determined duty cycle to a duty cycle threshold, which canbe selected from the range between 1% or less and 50% or more. Thecomparison can, for example, indicate presence of a leak in the system.In other words, if the pump is remains active over a period of time sothat the duty cycle threshold is reached or exceeded, the pump may beworking hard to overcome the leak. In such cases, the negative pressuresource can be configured to suspend or pause the delivery of therapy.The negative pressure source can be configured to provide an indicationto the user that the pump is working hard (e.g., duty cycle exceeds theduty cycle threshold) by, for example, deactivating the source ofnegative pressure. In some embodiments, the duty cycle threshold can bea preset value, set or changed by the user, and/or varied based onvarious operating conditions or on any combination thereof. As isillustrated in FIG. 3, the negative pressure source can be configured tocompare the determined duty cycle to the duty cycle threshold (e.g., 9%or another suitable fixed or dynamic threshold). The negative pressuresource can be configured to monitor the number of duty cycles thatexceed the threshold by, for example, maintaining and updating anoverload counter, which can be reset when the negative pressure sourcetransitions from state 1252 to the IPD state 1260.

In some embodiments, the negative pressure source can be configured toupdate the overload counter in state 1300. If the determined duty cycledoes not exceed the duty cycle threshold, the negative pressure sourcecan decrement the overload counter. In some embodiments, the minimumvalue of overload counter can be set to zero, that is the overloadcounter cannot become negative. Conversely, if the determined duty cycleis equal to or exceeds the duty cycle threshold, the negative pressuresource can increment the overload counter.

In some embodiments, the negative pressure source can be configured tomonitor a total or aggregate number of duty cycles that equal to orexceed the duty cycle threshold. This approach can help to smooth oraverage the duty cycle variation in order to, for example, prevent oneor several erratic cycles that may be caused by a transient leak frominterrupting therapy. In some embodiments, the negative pressure sourcecan be configured to monitor consecutive or non-consecutive duty cyclesexceeding the duty cycle threshold. In some embodiments, the thresholdcan be a preset value, set or changed by the user, and/or varied basedon various operating conditions or on any combination thereof. If thenumber of duty cycles that exceed the duty cycle threshold is determinedto exceed an overload threshold (e.g., a number between 1 and 60 ormore, such as 30), the negative pressure source can be configured tomake the transition 1230 to the paused state 1216, where therapy issuspended or paused as is described herein. In some embodiments, thenegative pressure source can be configured to deactivate the source ofnegative pressure, which can provide an indication to the user that thepump is working hard (e.g., duty cycle exceeds the overload threshold).If the number of duty cycles that exceed the duty cycle threshold is notdetermined to exceed the overload threshold, the negative pressuresource can be configured to make the transition 1304 and remain in theoperational state category 1250. In some embodiments, the negativepressure source can be configured to return to the same state and/ortransition between states from which the negative pressure source madethe transition 1302. In some embodiments, the negative pressure sourcecan be configured to transition to a different state and/or transitionbetween states.

In some embodiments the negative pressure source is further configuredto suspend or pause therapy if the user presses the button 1002 whilethe negative pressure source is in the operational state category 1250.In some embodiments, the negative pressure source can be configured totransition to the manually paused state 1216.

FIG. 4 illustrates another state diagram of operation of the negativepressure source 104 according to some embodiments. In some embodiments,the controller can be configured to implement the flow of the statediagram 1400. In some embodiments, the flow 1400 can be largely similarto the flow illustrated in FIGS. 2-3. State 1402 corresponds to state1202, state 1406 corresponds to state 1260, state category 1410corresponds to state category 1210, state 1414 corresponds to state1214, state 1416 corresponds to state 1216, state 1418 corresponds tostate 1218, transition 1420 corresponds to transition 1220, transition1422 corresponds to transition 1222, transition 1424 corresponds to thetransition 1224, transition 1426 corresponds to transition 1226, state1440 corresponds to state 1240, and state 1459 corresponds to the state1259. In addition, state category 1450 corresponds to state category1250, state 1460 corresponds to state 1260, transition 1464 correspondsto transition 1264, state 1466 corresponds to transition 1266,transition 1468 corresponds to transition 1268, transition 1428 acorresponds to transition 1228 a, state 1470 corresponds to state 1270,and transition 1472 corresponds to transition 1272. Further, transition1476 corresponds to transition 1276, state 1480 corresponds to state1280, transition 1482 corresponds to transition 1282, state 1490corresponds to state 1290, transition 1492 corresponds to transition1292, state 1494 corresponds to state 1294, transition 1496 correspondsto transition 1296, transition 1428 b corresponds to transition 1228 b,transition 1512 corresponds to transition 1312, transition 1514corresponds to transition 1314, and transition 1516 corresponds totransition 1316.

In some embodiments, the negative pressure source can be configured tomonitor the duty cycle after a desired negative pressure level isestablished in the fluid flow path in the MPD state 1490. In someembodiments, the negative pressure source can also take into account theduration of time that the pump has been active while the negativepressure source remains in the IPD state 1460. As is illustrated, thedevice can be configured to make the transition 1484 from the MPD state1490. Transition 1484 can be similar to the transition 1284, but insteadof transitioning directly to the IPD state 1480, the negative pressuresource can be configured to monitor the duty cycle in state 1500. Insome embodiments, the negative pressure source can be configured tomonitor the duty cycle during a cumulative period of time that thenegative pressure source has remained in the monitor state 1480 and MPDstate 1490. In some embodiments, the negative pressure source can beconfigured to monitor the duty cycle over the cumulative period of timeduring the immediately preceding or previous monitor and MPD cycles. Forexample, immediately before transitioning to state 1500 the negativepressure source could have remained in the MPD state 1490 for timeduration X (during which the pump was active). In addition, assumingthat immediately before transitioning to the MPD state 1490, thenegative pressure source remained in the monitor state 1480 for a timeduration Y (during which the pump was not active), the duty cycle (DC)can be expressed (e.g., in percent) as:

DC=100%*[X/(X+Y)].  (3)

In order to determine the duty cycle, the negative pressure source canbe configured to monitor the duration of time that the pump has beenactive and/or inactive.

In some embodiments, the negative pressure source can be configured tocompare the determined duty cycle to a duty cycle threshold, as isdescribed herein. In some embodiments, the threshold can be a presetvalue, set or changed by the user, and/or varied based on variousoperating conditions or on any combination thereof. If the duty cycle isdetermined to be below the threshold, the negative pressure source canbe configured to make the transition 1502 to the monitor state 1480.Conversely, if the duty cycle is determined to be equal to or exceed thethreshold, the negative pressure source can be configured to make thetransition 1504 to state 1506. In some embodiments, the negativepressure source can provide an indication that the duty cycle exceedsthe threshold by, for example, deactivating the pump.

In some embodiments, the negative pressure source can be configured tomonitor a total or aggregate time over which the duty cycle is equal toor exceeds the threshold. This approach can help to smooth or averagethe duty cycle variation in order to, for example, prevent one orseveral erratic cycles that may be caused by a transient leak frominterrupting therapy. Monitoring can be accomplished by maintaining atimer (in firmware, software, hardware or any combination thereof),which can be restarted (e.g., on the transition 1476) and updated (e.g.,in state 1506). In some embodiments, the negative pressure source can beconfigured to determine whether the duty cycle equals to or exceeds thethreshold over a certain aggregate period of time, which can be comparedto an aggregate duration threshold. The threshold can be selected from arange between 5 minutes or less and 2 hours or more, such as 30 minutes.In some embodiments, the threshold can be a preset value, set or changedby the user, and/or varied based on various operating conditions or onany combination thereof. If the aggregate period of time equals to orexceeds the threshold, the negative pressure source can be configured tomake the transition 1508 to the paused state 1418, where the negativepressure source can be configured to suspend or pause the delivery oftherapy. In some embodiments, the negative pressure source can indicatethis transition to the user by, for example, deactivating the pump.Conversely, if the aggregate period of time is determined to be lessthan the threshold, the negative pressure source can be configured tomake the transition 1510 to the monitor state 1480. The pump assemblycan be configured to indicate the transition 1510 to the user by, forexample, causing the OK indicator to blink or flash and deactivating thedressing indicator.

Other Variations

Additional embodiments of controlling the negative pressure source asdescribed in U.S. Pat. No. 8,905,985, the entirety of which isincorporated herein by reference. Additional embodiments of calibratingthe drive signal of a pump are described in PCT Publication No. WO2016103035, the entirety of which is incorporated herein by reference.The embodiments described herein are compatible with and can be part ofthe embodiments described in these publications, and some or all of thefeatures described herein can be used or otherwise combined with any ofthe features described in these publications.

Any value of a threshold, limit, duration, etc. provided herein is notintended to be absolute and, thereby, can be approximate. In addition,any threshold, limit, duration, etc. provided herein can be fixed orvaried either automatically or by a user. Furthermore, as is used hereinrelative terminology such as exceeds, greater than, less than, etc. inrelation to a reference value is intended to also encompass being equalto the reference value. For example, exceeding a reference value that ispositive can encompass being equal to or greater than the referencevalue. In addition, as is used herein relative terminology such asexceeds, greater than, less than, etc. in relation to a reference valueis intended to also encompass an inverse of the disclosed relationship,such as below, less than, greater than, etc. in relations to thereference value. Moreover, although blocks of the various processes maybe described in terms of determining whether a value meets or does notmeet a particular threshold, the blocks can be similarly understood, forexample, in terms of a value (i) being below or above a threshold or(ii) satisfying or not satisfying a threshold.

Features, materials, characteristics, or groups described in conjunctionwith a particular aspect, embodiment, or example are to be understood tobe applicable to any other aspect, embodiment or example describedherein unless incompatible therewith. All of the features disclosed inthis specification (including any accompanying claims, abstract anddrawings), or all of the steps of any method or process so disclosed,may be combined in any combination, except combinations where at leastsome of such features or steps are mutually exclusive. The protection isnot restricted to the details of any foregoing embodiments. Theprotection extends to any novel one, or any novel combination, of thefeatures disclosed in this specification (including any accompanyingclaims, abstract and drawings), or to any novel one, or any novelcombination, of the steps of any method or process so disclosed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of protection. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms. Furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made. Those skilled in the art willappreciate that in some embodiments, the actual steps taken in theprocesses illustrated or disclosed may differ from those shown in thefigures. Depending on the embodiment, certain of the steps describedabove may be removed, others may be added. For example, the actual stepsor order of steps taken in the disclosed processes may differ from thoseshown in the figure. Depending on the embodiment, certain of the stepsdescribed above may be removed, others may be added. For instance, thevarious components illustrated in the figures may be implemented assoftware or firmware on a processor, controller, ASIC, FPGA, ordedicated hardware. Hardware components, such as processors, ASICs,FPGAs, and the like, can include logic circuitry. Furthermore, thefeatures and attributes of the specific embodiments disclosed above maybe combined in different ways to form additional embodiments, all ofwhich fall within the scope of the present disclosure.

User interface screens illustrated and described herein can includeadditional or alternative components. These components can includemenus, lists, buttons, text boxes, labels, radio buttons, scroll bars,sliders, checkboxes, combo boxes, status bars, dialog boxes, windows,and the like. User interface screens can include additional oralternative information. Components can be arranged, grouped, displayedin any suitable order.

Although the present disclosure includes certain embodiments, examplesand applications, it will be understood by those skilled in the art thatthe present disclosure extends beyond the specifically disclosedembodiments to other alternative embodiments or uses and obviousmodifications and equivalents thereof, including embodiments which donot provide all of the features and advantages set forth herein.Accordingly, the scope of the present disclosure is not intended to belimited by the specific disclosures of preferred embodiments herein, andmay be defined by claims as presented herein or as presented in thefuture.

Conditional language, such as “can,” “could,” “might,” or “may,” unlessspecifically stated otherwise, or otherwise understood within thecontext as used, is generally intended to convey that certainembodiments include, while other embodiments do not include, certainfeatures, elements, or steps. Thus, such conditional language is notgenerally intended to imply that features, elements, or steps are in anyway required for one or more embodiments or that one or more embodimentsnecessarily include logic for deciding, with or without user input orprompting, whether these features, elements, or steps are included orare to be performed in any particular embodiment. The terms“comprising,” “including,” “having,” and the like are synonymous and areused inclusively, in an open-ended fashion, and do not excludeadditional elements, features, acts, operations, and so forth. Also, theterm “or” is used in its inclusive sense (and not in its exclusivesense) so that when used, for example, to connect a list of elements,the term “or” means one, some, or all of the elements in the list.Further, the term “each,” as used herein, in addition to having itsordinary meaning, can mean any subset of a set of elements to which theterm “each” is applied.

Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, or Z. Thus, such conjunctive language is not generallyintended to imply that certain embodiments require the presence of atleast one of X, at least one of Y, and at least one of Z.

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than 10% of, within less than 5% of, within less than 1% of, withinless than 0.1% of, and within less than 0.01% of the stated amount. Asanother example, in certain embodiments, the terms “generally parallel”and “substantially parallel” refer to a value, amount, or characteristicthat departs from exactly parallel by less than or equal to 15 degrees,10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degree.

The scope of the present disclosure is not intended to be limited by thespecific disclosures of preferred embodiments in this section orelsewhere in this specification, and may be defined by claims aspresented in this section or elsewhere in this specification or aspresented in the future. The language of the claims is to be interpretedbroadly based on the language employed in the claims and not limited tothe examples described in the present specification or during theprosecution of the application, which examples are to be construed asnon-exclusive.

1. A negative pressure wound therapy apparatus comprising: a negativepressure source configured to provide negative pressure via a fluid flowpath to a dressing placed over a wound to create a seal over the wound;a pressure sensor configured to measure pressure in the fluid flow path;and a controller configured to, in response to a request to initiate orrestart application of negative pressure: operate the negative pressuresource in a first mode to provide negative pressure to the wound;determine a change in pressure in the fluid flow path over a period oftime based on a plurality of measurements by the pressure sensor overthe period of time; in response to a determination that pressure in thefluid flow path is becoming more negative, operate the negative pressuresource in a second mode in which the negative pressure source provides agreater amount of negative pressure than in the first mode; and inresponse to a determination that pressure in the fluid flow path is notbecoming more negative, provide an indication of a first leak in theseal.
 2. The apparatus of claim 1, wherein: the request to initiate orrestart application of negative pressure is associated with a negativepressure set point to be established in the fluid flow path; operationof the negative pressure source in the first mode is insufficient toreduce pressure in the fluid flow path to establish the negativepressure set point; and operation of the negative pressure source in thesecond mode is sufficient to reduce pressure in fluid flow path toestablish the negative pressure set point.
 3. The apparatus of claim 2,wherein operation of the negative pressure in the second mode comprisesthe controller being further configured to: activate the negativepressure source to reduce pressure in the fluid flow path to thenegative pressure set point; if pressure in the fluid flow path has notreached the negative pressure set point over a first period of time,deactivate the negative pressure source for a second period of time; andin response to a determination that the second period of time haselapsed, activate the negative pressure source to reduce pressure in thefluid flow path to establish the negative pressure set point.
 4. Theapparatus of claim 3, wherein the controller is further configured tomonitor a number of deactivations of the negative pressure source forthe second period of time.
 5. The apparatus of claim 4, wherein thecontroller is further configured to provide an indication of a secondleak in the seal in response to a determination that the number of thenegative pressure source exceeds a retry threshold.
 6. The apparatus ofclaim 5, wherein the first leak comprises a leak of smaller intensitythan the second leak.
 7. The apparatus of claim 5, wherein theindication of at least one of the first or second leaks in the sealcomprises deactivation of the source of negative pressure.
 8. Theapparatus of claim 1, wherein operation of the negative pressure sourcein the first mode comprises establishment of a flow rate of about 25mL/min in the fluid flow path.
 9. The apparatus of claim 8, wherein theindication of the first leak in the seal corresponds to an indication ofa leak with flow of about 25 mL/min or less.
 10. The apparatus of claim1, wherein the controller is configured to determine the change inpressure in the fluid flow path based on a determination of a differencein a first pressure in the fluid flow path measured by the pressuresensor and a second pressure in the fluid flow path subsequentlymeasured by the pressure sensor.
 11. The apparatus of claim 1, whereinthe first mode comprises a low flow mode in which the negative pressuresource provides a lower flow rate in the fluid flow path than in thesecond mode.
 12. The apparatus of claim 1, wherein the controller isconfigured to operate the negative pressure source in the first modebased on a first drive signal provided to an actuator of the negativepressure source.
 13. The apparatus of claim 12, wherein the controlleris configured to operate the negative pressure source in the second modebased on a second drive signal provided to the actuator of the negativepressure source, the second drive signal being different from the firstdrive signal.
 14. A method of operating a negative pressure woundtherapy apparatus, the method comprising: by a controller, in responseto a request to initiate or restart application of negative pressure:operating a negative pressure source in a first mode and providingnegative pressure, the negative pressure source configured to providenegative pressure via a fluid flow path to a dressing placed over awound to create a seal over the wound; determining a change in pressurein the fluid flow path over a period of time based on a plurality ofmeasurements by a pressure sensor over the period of time; in responseto determining that pressure in the fluid flow path is becoming morenegative, operating the negative pressure source in a second mode inwhich the negative pressure source provides a greater amount of negativepressure than in the first mode; and in response to determining thatpressure in the fluid flow path is not becoming more negative, providingan indication of a first leak in the seal.
 15. The method of claim 14,wherein: the request to initiate or restart application of negativepressure is associated with a negative pressure set point to beestablished in the fluid flow path; operating the negative pressuresource in the first mode is insufficient to reduce pressure in the fluidflow path to establish the negative pressure set point; and operatingthe negative pressure source in the second mode is sufficient to reducepressure in fluid flow path to establish the negative pressure setpoint.
 16. The method of claim 15, wherein operating the negativepressure in the second mode further comprises: activating the negativepressure source to reduce pressure in the fluid flow path to thenegative pressure set point; if pressure in the fluid flow path has notreached the negative pressure set point over a first period of time,deactivating the negative pressure source for a second period of time;and in response to determining that the second period of time haselapsed, activating the negative pressure source to reduce pressure inthe fluid flow path to establish the negative pressure set point. 17.The method of claim 16, further comprising monitoring a number ofdeactivations of the negative pressure source for the second period oftime.
 18. The method of claim 17, further comprising providing anindication of a second leak in the seal in response to determining thatthe number of the negative pressure source exceeds a retry threshold.19. The method of claim 18, wherein the first leak comprises a leak ofsmaller intensity than the second leak.
 20. The method of claim 18,wherein the indication of at least one of the first or second leaks inthe seal comprises deactivating the source of negative pressure.
 21. Themethod of claim 14, wherein operating the negative pressure source inthe first mode comprises establishing a flow rate of about 25 mL/min inthe fluid flow path.
 22. The method of claim 21, wherein the indicationof the first leak in the seal corresponds to an indication of a leakwith flow of about 25 mL/min or less.
 23. The method of claim 14,wherein determining the change in pressure in the fluid flow path isfurther based on determining a difference in a first pressure in thefluid flow path measured by the pressure sensor and a second pressure inthe fluid flow path subsequently measured by the pressure sensor. 24.The method of claim 14, wherein the first mode comprises a low flow modein which the negative pressure source provides a lower flow rate in thefluid flow path than in the second mode.
 25. The method of claim 14,wherein operating the negative pressure source in the first mode furthercomprises providing a first drive signal to an actuator of the negativepressure source.
 26. The method of claim 25, further operating thenegative pressure source in the second mode further comprises providinga second drive signal to the actuator of the negative pressure source,the second drive signal being different from the first drive signal.